WASHINGTON- A blizzard producing heavy snow and powerful winds pummelled the U.S. mid-Atlantic on Saturday, causing at least two fatalities and paralyzing travel in the region.

Snowfall totals of 20 to 30 inches (51 to 76 cm) are forecast from Virginia to southern New Jersey by Saturday evening when the storm is expected to move out to sea.

Up to 23 inches (53 cm) of snow had fallen by 6 a.m. EST (11 a.m. British time) in suburban Washington, D.C. Local weather forecasters said the storm could bring the heaviest snowfall in 90 years to the Washington area. Thirty inches of snow were reported in Shenandoah, Virginia, 120 miles (193 km) west of Washington.

The National Weather Service declared a 24-hour blizzard warning for the Washington-Baltimore region until 10 p.m. EST Saturday/3 a.m. British time Sunday.

Winds were strong, especially along the mid-Atlantic coast, with gusts recorded up to 40 mph (64 kph).

Virginia state police reported two people were killed in Virginia when they were struck by a tractor-trailer after stopping to help a stranded motorist.

Most flights were cancelled on Saturday at the Washington-Baltimore area's three main airports and at Philadelphia International Airport.

Driving in the region was treacherous and authorities advised motorists to stay off the roads.

Washington's Metro train service was operating only underground on Saturday and bus service was cancelled.

Amtrak cancelled a number of trains operating on Saturday between New York and Washington and also between Washington and some destinations to the south.

More than 180,000 homes lost power in the Washington area as the wet and heavy snow weighed down trees and power lines.

The storm brought school closings and long lines at supermarkets on Friday as frenzied area residents rushed to stock up on groceries and other supplies ahead of a traditional party weekend for watching Sunday's Super Bowl football game.

Virginia, Maryland, the District of Columbia each declared snow emergencies, allowing them to activate emergency agencies, including the National Guard, to help prepare for the wintry onslaught and cope with its aftermath.

The storm prompted U.S. government offices in the Washington area to close four hours early on Friday.

The Smithsonian museums and the National Zoo were closed Saturday in Washington.

Unseasonably cold temperatures were expected in the storm's wake next week in the U.S. Northeast, which is the world's biggest heating oil market, and the Midwest, a large natural gas demand centre.

The cold helped boost New York's spot natural gas market towards winter season highs on Friday, where prices reached about $11.50 per million British thermal units on average, up more than $4 from Thursday.

Spot gas for Chicago rose 10 cents to above $5.70. Meanwhile, heating oil was little changed.
Once we get through the weekend storm, much colder air will invade the Northeast and mid-Atlantic. The outlook for the northeast third of the country next week is looking much colder than normal, said Jim Rouiller, a senior energy meteorologist at private weather forecaster Planalytics.

The same weather system brought heavy rains to parts of the southeastern United States including the Carolinas and Georgia while fuelling itself with fresh moisture from the Gulf of Mexico and the Atlantic Ocean.

(Reporting by David Morgan and Eric Beech; additional reporting by Ed McAllister and Eileen Moustakis in New York; Editing by Jon Hemming and Bill Trott)